1. Field of the Invention
The present invention relates to the microbial fermentation industry, more precisely, a technique of imparting an ability to utilize methanol to a microorganism not originally having such an ability or enhancing such an ability of a microorganism having such an ability at a low level and a method for producing a target substance by utilizing methanol with use of a microorganism obtained by such a technique as mentioned above.
Substances produced according to the present invention include L-amino acids, nucleic acids, antibiotics, vitamins, growth factors, physiologically active substances and so forth, which have conventionally been produced by using microorganisms.
2. Description of the Related Art
To date, most of fermentation raw materials utilized in production of useful substances by microbial fermentation are sugars derived from agricultural products. However, since prices of sugars derived from agricultural products are considered to be on an upward trend in future, an inexpensive material of good quality is desired as an alternative fermentation raw material.
Methanol is easily dissolved in water and inexpensive, and it can be obtained at a high purity. Moreover, it can be comparatively easily produced from methane, which is a main component of natural gas. Therefore it is attractive as a raw material for substance production. If methanol is used as a raw material for microbial fermentation, not only the cost of the main raw material can be reduced, but also purification of products from fermentation solutions and waste solution disposal process can be simplified. Thus, the total production cost can be reduced.
As methods for producing substances, especially amino acids, from methanol as a raw material by utilizing microorganisms, there have been already known a method of utilizing a microorganism of the genus Achromobacter or Pseudomonas (Japanese Patent Publication (Kokoku) No. 45-25273), a method of utilizing a microorganism of the genus Protaminobacter or Methanomonas (Japanese Patent Laid-open Publication (Kokai) No. 50-25790), a method of utilizing a microorganism of the genus Methylobacillus (Japanese Patent Laid-open Publication No. 4-91793), a method of utilizing a methylotrophic bacterium belonging to the genus Bacillus (Japanese Patent Laid-open Publication No. 3-505284, U.S. Pat. No. 6,083,728) and so forth. However, all the bacterial strains have not acquired high productivity of amino acids acceptable as bacteria for practical use.
Meanwhile, methods of utilizing microorganisms of the genus Brevibacterium, Corynebacterium, Bacillus or Escherichia constitute the mainstream of methods for producing amino acids from glucose (“Amino Acid Fermentation”, Ed. by H. Aida et al., Gakkai Shuppan Center). These amino acid producing bacteria are precious bacterial strains bred by introducing various mutations in order to obtain the maximum productivity of amino acids during the long history from the discovery thereof to the breeding of practically useful strains. However, these industrially used strains are microorganisms that cannot utilize methanol.